Track trencher information system and process

ABSTRACT

A system for acquiring and displaying information associated with the operational conditions of a track trencher excavation machine. A plurality of informational messages indicative of one of a plurality of operating conditions of the track trencher are selectively communicated to an operator over a display. Data acquired from a plurality of track trencher sensors is processed and interpreted by a computer to provide status, diagnostic, safety, and instructional messages to an operator in an immediately understandable format.

FIELD OF THE INVENTION

The present invention relates generally to the field of excavation and,more particularly, to a system and process for acquiring andcommunicating information indicative of track trencher operation.

BACKGROUND OF THE INVENTION

A track trencher excavation machine, shown in FIGS. 1 and 2, typicallyincludes an engine 36 coupled to a right track drive 32 and a left trackdrive 34 which together comprise the tractor portion 45 of the tracktrencher 30. An attachment 46, usually coupled to the front of thetractor portion 45, typically performs a specific type of excavatingoperation.

A ditcher chain 50 is often employed to dig relatively large trenches atan appreciable rate. The ditcher chain 50 generally remains above theground in a transport configuration 56 when maneuvering the trencher 30around the work site. During excavation, the ditcher chain 50 islowered, penetrates the ground, and excavates a trench at the desireddepth and speed while in a trenching configuration 58. Another populartrenching attachment is termed a rock wheel in the art, shown in FIG. 3,and may be controlled in a manner similar to that of the ditcher chain50.

A track trencher excavation machine typically employs one or moresensors that monitor various physical parameters of the machine, andmeans for altering machine operations in an attempt to increaseexcavation productivity. The information gathered from the sensors isgenerally used to moderate a particular machine function, or to providethe operator with information typically by transducing a sensor signalfor communication to one or more analog display instruments, such as atachometer, for example. The information communicated to an operator byemploying a plurality of conventional analog display instruments mustgenerally be interpreted by a skilled operator in order to assesswhether the track trencher is operating within acceptable performanceand safety margins.

FIG. 4 is an illustration of a conventional control panel 62 of a tracktrencher 30. Propulsion and steering of a track trencher 30 whenoperating in a transport mode is generally controlled by manipulatingthe left and right track levers 64 and 66 which respectively controlactuation of the left and right track drives 34 and 32. The prior artcontrol panel 62 includes a speed range switch 74, RPM knob 76, steeringtrim knob 78, and propel trim knob 80, all of which are typicallyadjusted during normal trenching operation of a track trencher 30. Ahigh degree of skill is typically required on the part of the operatorwho must continuously monitor the effects of adjustments made to thepropulsion and steering of the tractor portion 45, as well as theeffects on the operation of the attachment 46. Maintaining optimum tracktrencher performance using the controls and analog display instrumentsof a prior art control panel 62 during both excavation and transport isgenerally considered an exacting and fatiguing task.

It can be appreciated that the complex task of operating a tracktrencher 30 is further complicated by the necessity to read, interpret,and assess the information provided by a plurality of prior art analogdisplay instruments. The limited nature and amount of informationprovided by the plurality of prior art analog display instruments shownin FIG. 4 is typically used by the operator when adjusting theaforementioned controls in an attempt to efficiently control the tracktrencher 30.

When operating a track trencher 30 in a trench mode during excavation,for example, a tachometer 72 is typically employed to monitor the speedat which the engine 36 is operating. An operator is typically alerted tochanges in the loading of the engine 36 during excavation by associatedchanges in engine speed reflected on the tachometer 72. The operator,however, cannot determine the speed at which the track trencher isexcavating, the speed at which the trenching attachment 46 is operating,and degree of turning in either the left or right direction. Suchdeterminations, if made at all, are mere estimates, the accuracy ofwhich is highly dependent on the experience level of an operator.

It is often desirable to determine an optimum track trencher andattachment speed for excavating a particular excavation site and, at alater time, the next working day for example, return to the same optimumlevels to increase overall trenching efficiency. Further, depending onthe particular topography of an area to be excavated, the operator maybe required to steer the track trencher 30 in a direction to excavateone or more curved trenches. The prior art analog display instruments ofa conventional control panel 62 provide insufficient information fordetermining such optimum trenching speeds and directions.

There is a desire among the manufacturers of track trenchers to minimizethe difficulty of operating a track trencher, and to reduce thesubstantial amount of time currently required to adequately train atrack trencher operator. Further, there continues to exist in theexcavation equipment manufacturing community a keenly felt need toenhance the means of communicating operational, diagnostic, andsafety-related information to the operator during track trencheroperation. The present invention fulfills these needs.

SUMMARY OF THE INVENTION

The present invention is a data acquisition and display system andprocess for communicating to an operator informational messagesindicative of one of a plurality of operational conditions of a tracktrencher. The invention also includes means for selectively displayingthe informational messages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a track trencher, including a ditcher chaintrenching attachment;

FIG. 2 is a generalized top view of a track trencher;

FIG. 3 is a side view of a track trencher with a rock wheel trenchingattachment coupled thereto;

FIG. 4 is an illustration of a prior art control panel for controlling atrack trencher;

FIG. 5 is a fragmentary view of a prior art control panel illustratingthe levers and controls required to operate a conventional tracktrencher;

FIG. 6 is a fragmentary view of a track trencher control panelincorporating a novel multiple mode propel control and multiple modesteering control;

FIG. 7 is a full view of a track trencher control panel incorporatingmultiple mode propel and steering controls and a display;

FIG. 8 is an illustration of a multiple mode propel control andassociated functions when operating a track trencher in a trench modeand a transport mode;

FIG. 9 is a graph illustrating the output level of the left and righttrack drives of a track trencher in response to propel control outputvoltage signals when a speed range control is set to a high setting;

FIG. 10 is a graph illustrating the output level of the left and righttrack drives of a track trencher in response to propel control outputvoltage signals when a speed range control is set to a low setting;

FIG. 11 is a graph illustrating a productive range of target engineoutput levels associated with a partial re-calibration procedure duringtrenching operation;

FIG. 12 is an illustration of a prior art steering control apparatuscomprising independent left and right track levers;

FIG. 13 is a graphical illustration of a novel multiple mode steeringcontrol and its operation in both a transport mode and a trench mode;

FIG. 14 is a graph illustrating the left and right track drive steeringcharacteristics of a track trencher operating in a trench mode when anovel multiple mode steering control is employed;

FIG. 15 is a graph illustrating the left and right track drive steeringcharacteristics of a track trencher operating in a transport mode when amultiple mode steering control is employed;

FIG. 16 is a graphical illustration of the intuitive steering capabilityprovided by a novel multiple mode steering control;

FIG. 17 is a block diagram illustrating a computer system forcontrolling the propulsion and steering of a track trencher employingmultiple mode propel and steering controls;

FIG. 18 illustrates examples of various status and fault messagescommunicated to the operator of a track trencher over a display;

FIG. 19 is an illustration of a novel multiple mode throttle control;

FIG. 20 illustrates an alternative configuration of a novel multiplemode steering control;

FIG. 21 illustrates a first part of a control process for modifyingtrack drive propulsion levels in response to transport propel signalsproduced by a novel multiple mode propel control;

FIG. 22 illustrates a second part of a control process for modifyingtrack drive propulsion levels in response to transport propel signalsproduced by a novel multiple mode propel control;

FIG. 23 illustrates a first part of a control process for modifyingtrack drive propulsion levels in response to trench propel signalsproduced by a novel multiple mode propel control;

FIG. 24 illustrates a second part of a control process for modifyingtrack drive propulsion levels in response to trench propel signalsproduced by a novel multiple mode propel control;

FIG. 25 illustrates a first part of a control process for effectuatingsteering of a track trencher operating in a transport node in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 26 illustrates a second part of a control process for effectuatingsteering of a track trencher operating in a transport mode in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 27 illustrates a third part of a control process for effectuatingsteering of a track trencher operating in a transport node in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 28 illustrates a fourth part of a control process for effectuatingsteering of a track trencher operating in a transport mode in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 29 illustrates a fifth part of a control process for effectuatingsteering of a track trencher operating in a transport node in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 30 illustrates a sixth part of a control process for effectuatingsteering of a track trencher operating in a transport mode in responseto steering control signals produced by a novel multiple mode steeringcontrol;

FIG. 31 illustrates a first part of a control process for effectuatingsteering of a track trencher operating in a trench mode in response tosteering control signals produced by a novel multiple mode steeringcontrol; and

FIG. 32 illustrates a second part of a control process for effectuatingsteering of a track trencher operating in a trench mode in response tosteering control signals produced by a novel multiple mode steeringcontrol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention, as previously indicated, relates to aninformation system and process for a track trencher. The presentapplication describes the entire system and process for controllingpropulsion and steering, and communicating to an operator theoperational status of a track trencher in order to permit a completeappreciation of the various functions and activities within the system.As such, there are described in the present application various featuresand functions of the track trencher propulsion and steering controlsystem which are not the subject of the present invention, but are thesubject of inventions claimed in co-pending applications fileconcurrently with this application. The description of these featuresand functions are included in the present application for completenessand to permit a full appreciation of the operation of the track trencherpropulsion and steering control system disclosed herein.

Referring now to the figures, and more particularly to FIG. 7, there isshown a control panel 101 including a novel display 100 forcommunicating to an operator a plurality of informational messagesindicative of a plurality of operating conditions of a track trencher30. The control panel 101 also includes novel multiple mode propel andsteering controls 90 and 92 for controlling the propulsion and steeringof a track trencher 30. In one embodiment, the propel control 90,steering control 92, and travel mode control 94 operate in combinationto effectively propel and steer a track trencher 30 in one of aplurality of travel modes. The propel control 90 and steering control 92are preferably multiple mode controls, with each control 90 and 92performing a plurality of functions depending on a selected travel mode.

Comparing the novel control panel shown in FIG. 6 to a prior art controlpanel as shown in FIG. 5, it is readily apparent that the multiple modepropel and steering controls 90 and 92 illustrated in FIG. 6 provide fora substantial reduction in the number of control levers, switches, andtrimming knobs Otherwise required to operate a track trencher 30employing a prior art control scheme. Most noticeably, the two prior arttrack drive levers 64 and 66 have been eliminated, as well as atachometer 72 which is typically required to monitor the effects ofcontrol adjustments on the output level of the engine 36. Moreover, manyof the functions associated with the speed range switch 74, RPM knob 76,steering trim knob 78, and propel trim knob 80 of a prior art controlpanel 62, as shown in FIG. 5, are either eliminated or integrated intothe functions performed by the unique multiple mode propel and controls90 and 92 illustrated in FIG. 6.

A prior art system for controlling a track trencher 30, as shown in FIG.5, typically includes a left track lever 64 and a right track lever 66which control both steering and propulsion of a track trencher 30. Theleft track lever 64 typically controls the actuation of the left trackdrive 34, while the right track lever 66 controls the actuation of theright track drive 32. As such, control of the left track drive 34 iswholly independent from that of the right track drive 32. Accordingly,an operator must continuously adjust the left and right track levers 64and 66 to properly steer and propel track trencher 30, in addition tofine tuning steering and propulsion operations using RPM knob 76, propeltrim knob 80, steering trim knob 78, and speed range switch 74.

One important advantage of the novel control scheme illustrated in FIGS.6 and 7 concerns the effective uncoupling, or separating, of thesteering control functions from the propulsion control functions forcontrolling a track trencher 30. Propulsion of the left and right trackdrives 34 and 32 is controlled by the propel control 90, while steeringof a track trencher 30 is independently controlled by the steeringcontrol 92. Controlling a track trencher 30 while operating in any oneof a plurality of travel modes is substantially simplified by employingthe multiple mode propel and steering controls 90 and 92.

Referring now to FIG. 8, there is shown a multiple mode propel control90 for controlling propulsion of a track trencher 30 in one of aplurality of travel modes. By use of the term "multiple mode," it ismeant that a particular control performs a plurality of distinctfunctions depending on a particular selected mode of operation. As such,a plurality of control tasks, heretofore executed manually by anoperator of a track trencher 30, are instead performed by a singlemultiple mode control, such as the propel and steering controls 90 and92 shown in FIG. 8, which would otherwise be performed by manipulating amultiplicity of control levers, switches, and trimming knobs, aspreviously discussed.

The propel control 90 shown in FIG. 8 has a neutral setting, a maximumforward setting, a maximum reverse setting, and a range of forward andreverse settings. By way of illustration, and not of limitation, themultiple mode propel control 90 is preferably operable in a transportmode and a trench mode, it being understood that travel modes other thana transport and trench mode may be selectably available. Selection of atransport mode or a trench mode of operation is preferably determined bythe state of a travel mode control 94, which alters the functionality ofthe propel control 90.

In another embodiment, manual selection of a travel mode using a travelmode control 94 is eliminated. Transitioning to and from a trench modeand a transport mode may be accomplished by sensing the position of thethrottle 206 of the engine 36. In the embodiment shown in FIG. 19, thethrottle control 206 is operable in a transport range defined by aminimum throttle position 232 and a maximum throttle position 234.Operating the throttle control 206 within the transport range isinterpreted by the computer 182 as a selection of the transport travelmode.

Moving the throttle control 206 into the neutral range 236 isinterpreted by the computer 182 as requesting a transition out of thetransport or trench travel modes. Moving the throttle control 206 intothe trench mode range 238 effectively transitions the travel mode to thetrench mode. The trench mode is deselected by moving the throttlecontrol 206 back from the trench mode range 238 into the neutral range236. The transport mode may then be selected by moving the throttlecontrol 206 back to the minimum throttle position 232. It will beappreciated that the throttle control 206 configuration illustrated inFIG. 19 requires the operator to overtly change the positioning of thethrottle control 206 when transitioning between travel modes, therebydecreasing the probability of selecting an unintended travel mode.

In another embodiment, the throttle 206 includes a sensor coupled to theengine 36 which monitors the fuel being delivered to the engine 36. Thefuel control 204 preferably includes means for regulating the volume offuel delivered to the engine 36. A throttle sensor may be coupled to thefuel regulator and communicates the status of the fuel regulator to thecomputer 182. A maximum throttle control 206 setting, indicated bythrottle lever 230 being set to a maximum throttle position, isinterpreted by the computer 182 as a selection of the trench mode ofoperation. Throttle control 206 settings other than a maximum throttlecontrol position is interpreted by the computer 182 as a selection of atransport mode of operation. It is noted that the throttle control 206illustrated in FIG. 19 need not have separate transport and trenchranges. A single range of throttle control 206 settings may beappropriate, with a maximum throttle control setting being provided totransition the track trencher 30 between a transport mode and a trenchmode of operation.

In an alternative embodiment, the status of the attachment 46 is sensedand used as a basis for determined whether the transport mode or trenchmode is to be selected. An attachment sensor 186 preferably produces anattachment sense signal indicative of the operational status of theattachment 46. The computer 182 preferably interprets attachment 46activity as a selection of the trench travel mode, and attachment 46inactivity as a selection of the transport travel mode.

In one embodiment illustrated in FIG. 8, operating a track trencher 30in a transport mode is preferably accomplished by setting the travelmode control 94 to a transport mode setting. The forward and reversepropulsion of a track trencher 30 is preferably dependent on thepositioning of the propel control 90 between a forward and reversemaximum setting 122 and 124. The propel control 90 produces a transportpropel signal that is preferably proportional to the displacement of thepropel control 90 in either the forward or reverse direction withrespect to a neutral setting 120. Further, the transport propel signalis preferably representative of a target track motor speed measured inrevolutions-per-minute.

A neutral setting 120 is preferably associated with an idle state,whereby no power is delivered to the left and right track drives 34 and32. As the propel control 90 is moved in the forward direction,increasing power is proportionally transferred from the engine 36 to theleft and right track motors 42 and 44. A forward range 126 of propelcontrol 90 settings is defined between a neutral setting 120 and amaximum forward setting 122, with forward power being delivered to theleft and right track motors 42 and 44 in proportion to the forwarddisplacement of the propel control 90 within the forward range ofsettings 126. Similarly, a range of reverse settings 128 is definedbetween the neutral setting 120 and a maximum reverse setting 124. Poweris preferably applied to the left and right track motors 42 and 44 in areverse direction in proportion to the displacement of propel control 90within the reverse range of settings 128.

In another embodiment, setting the travel mode control 94 to a trenchmode setting causes the multiple mode propel control 90 to function in atrench mode. Operating the track trencher 30 in a trench mode typicallybegins by setting the propel control 90 to a neutral setting 110. Theoperator preferably then moves the propel control 90 to a maximumforward setting 112. At the maximum forward setting 112, the propelcontrol 90 produces a trench propel signal which is preferablyrepresentative of a target engine output level, or speed, measured inrevolutions-per-minute.

As discussed previously, it is generally desirable to maintain theengine 36 at a constant output level during excavation in a trench modewhich, in turn, allows the trenching attachment 46 to operate at anoptimum trenching output level. Controlling a track trencher 30 duringexcavation by employing a multiple mode propel control 90 shown in FIG.8 virtually eliminates the need for the operator to make any furtheradjustments to the propel control 90 in order to maintain the engine 36at a target engine output level. Rather, in response to a trench modesignal produced by the propel control 90 when set to a maximum forwardsetting 112, the propulsion levels of the left and right track motors 42and 44 are automatically modified by a computer 182, shown in FIG. 17and discussed in detail hereinafter, in order to maintain the engine 36at the target output level.

It may be desirable to modify the rate of excavation or, morespecifically, the loading on the engine 36 when operating a tracktrencher 30 in a trench mode. Another advantage of employing themultiple mode propel control 90 concerns the ability to modify theactual or the effective maximum forward setting 112 of the propelcontrol 90 during operation of the track trencher 30. A new or adjustedactual maximum forward setting is established by moving the propelcontrol 90 to a new maximum forward setting 116 after toggling a resetswitch 103, as shown in FIG. 7. Establishing a new or altered forwardmaximum setting 116 effectively results in the propel control 90producing a trench propel signal representative of a new target engineoutput level when the propel control 90 is set to the new alteredmaximum setting 112 during excavation. After selecting a new maximumforward setting 116, the reset switch 103 may be toggled back to itsoriginal position, and trenching may resume.

A new or adjusted target engine output level may alternatively beestablished by employing a unique user interface provided in part by thedisplay 100. Effective adjustment of the maximum forward setting 112 ispreferably accomplished by selecting a partial re-calibration menu forpresentation on the display 100. The partial recalibration menu ispreferably selected by actuation of the message selection switch 99. Anoperator typically moves the propel control 90 from the original maximumforward setting 112 to a neutral setting 120, and selects the partialre-calibration menu for presentation on the display 100 using themessage selection switch 99. The original target engine output levelwill preferably then be displayed on the display 100. Depressing are-calibration switch (not shown) preferably increases or decrease thevalue of the target engine output level to a new or adjusted targetengine output level. De-selection of the re-calibration switchpreferably results in replacing the original target engine output levelstored in the computer 182 with the new or adjusted target engine outputlevel. The operator may then move the propel control 90 from the neutralsetting 120 to the original maximum forward setting 112 to operate theengine at the new or adjusted target engine output level. Thus, themaximum forward setting 112 is effectively adjusted during a partialre-calibration procedure to operate the track trencher 30 at a new oradjusted target engine output level during excavation. In a preferredembodiment, an operator may select a new or adjusted target engineoutput level, measured in revolutions-per-minute, that is 100 RPMgreater than or less than the original target engine output level, andpreferably in increments of 25 RPM.

In another embodiment, the target engine output level, when operating atrack trencher 30 in the trench mode, is modifiable on-the-fly duringexcavation. The relationship between the output voltage signal of thepropel control 90 to a range of target output levels of the engine 36 isillustrated in FIG. 11. The engine load line 134 represents a spectrumof productive target engine output levels for a particular tracktrencher engine when operating in a trench mode. Adjusting the propelcontrol 90 to a new forward maximum setting 116 during excavation causesthe propel control 90 to produce a trench propel signal that results inan automatic readjustment of the target engine output level inaccordance with the engine load line 134.

A preferred target engine output level is generally associated with thespeed at which the engine 36 of a track trencher 30 produces maximumhorsepower, although other engine output levels may be appropriate.Depending on the particular engine characteristics of the track trencher30, the range of optimum engine speeds will differ. An example of atypical range of productive target engine output levels for a tracktrencher 30 is provided for illustrative purposes in FIG. 11.

In further reference to the engine load line 134, the engine 36, forexample, may be operated productively within a range of target engineoutput levels between 2,100 RPM to 2,450 RPM. At 2,100 RPM, the engine36 is considered to be heavily loaded and, in turn, generates maximumhorsepower, as well as maximum stress on the engine 30. At 2,450 RPM,loading of the engine 36 is considered minimal, thus generating minimumhorsepower with respect to the range of productive target engine outputlevels. Manual or on-the-fly adjustment of the target engine outputlevel to a new target engine output level in response to a trench propelsignal produced by the propel control 90 is preferably accomplished byadjusting the propel control 90 to a new or altered actual or effectivemaximum forward setting 116 between the neutral setting 110 and thepreviously established maximum forward setting 112. A track trencher 30operator, as discussed previously, need not make any further adjustmentsto the propel control 90 after selecting a new forward maximum settingwhen excavating in a trench mode.

An important advantage of operating a track trencher 30 using a multiplemode propel control 90 concerns additional functionality provided by aspeed range control 96, preferably having a high setting and a lowsetting. Turning now to FIGS. 9 and 10, there is shown two graphsillustrating a preferred relationship between the output of the propelcontrol 90 and the response of the left and right track drives 34 and32. The graph of FIG. 9 illustrates a relationship between the magnitudeof the left and right track drive 34 and 32 velocity, measured infeet-per-minute (FPM), in response to a selected propel control 90setting when the speed range control 96 is set to a high setting. FIG.10 illustrates a similar relationship when the speed range control 96 isset to a low setting.

The propel control 90 preferably produces a range of output voltagesignals between zero and 5.0 volts. A propel control 90 output voltagesignal of 2.5 volts is preferably associated with a neutral setting,wherein no power is delivered to the left and right track motors 42 and44. Forward propulsion is accomplished by moving the propel control 90in the forward direction, resulting in forward power being delivered tothe track motors 42 and 44. As shown in FIG. 9, a propel control 90output voltage signal of 5.0 volts typically is associated with amaximum forward track drive velocity, while an output voltage signal ofzero volts typically is associated with a maximum reverse track drivevelocity. In one embodiment, the magnitude of the maximum forward andreverse track drive velocities are 270 FPM when the high range settingof the speed range control 96 is selected, and 125 FPM when the lowrange is selected. Alternatively, a track trencher 30 may be operable inonly a single speed range. It will be understood that speed ranges otherthan high and low come within the scope of the track trencherinformation system invention.

The multiple mode steering control 92 provides additional advantageswhen operating a track trencher 30 in one of a plurality of travel mode.The steering control 92 shown in FIG. 13 effectively integrates into asingle control the steering functions performed by the two independenttrack levers 64 and 66, steering trim knob 78, and left and right pumppotentiometers 82 and 84 of a prior art control scheme shown in FIG. 12.Steering a track trencher 30 is typically accomplished by operating theleft and right track drives 34 and 32 at different velocities. Forexample, a prior art steering control system typically accomplishes leftturning by increasing the velocity of the right track drive 32, whilemaintaining or decreasing the velocity of the left track drive 34. Anoperator of a track trencher 30 must modify the relative velocities ofthe left and right track drives 34 and 32 to effectuate accurate turnsby continuously adjusting the prior art left and right track levers 64and 66, respectively. This task is substantially complicated since theprior art track levers 64 and 66 also control the propulsion of thetrack drives 34 and 32, respectively.

In stark contrast, the multiple mode steering control 92 provides asingle control for steering both the left and right track drives 34 and32. Moreover, the steering control 92 provides the operator of a tracktrencher 30 with a more natural or intuitive means for steering thetrack trencher 30, as discussed in greater detail with reference to FIG.16.

The multiple mode steering control 92, shown in FIGS. 13 and 20, isoperable in a plurality of steering modes, with the characteristics of aparticular steering mode being preferably alterable by selection of oneof a plurality of travel modes. In one embodiment, the steering control92 is a rotary control comprising a potentiometer, and having a neutralor zero setting 140 and a range of left and right settings. In anotherembodiment, the steering control 92 comprises a steering wheel havingsubstantially the same settings. The steering control 92 can preferablybe rotated through 150 degrees of left settings and 150 degrees of rightsettings with respect to the zero setting 140. The magnitude of left andright turning is preferably proportional to the degree to which thesteering control 92 is rotated from the zero setting 140 in the left andright directions, respectively.

Steering a track trencher 30 by employing the multiple mode steeringcontrol 92 illustrated in FIG. 13 differs fundamentally from the mannerin which steering is accomplished by prior art left and right tracklevers 64 and 66. Conventional left and right track levers 64 and 62independently steering an propel left and right track drives 34 and 32,with turning being accomplished typically by increasing the velocity ofone track drive relative to the other track drive. The steering control92, in contrast, controls the steering of a track trencher 30 preferablyby decreasing the velocity of only one track drive relative to the othertrack drive.

An important advantage of steering a track trencher 30 using thesteering control 92 concerns the manner in which steering isaccomplished when operating a track trencher 30 in a trench mode and atransport mode. When the travel mode control 94 is set to the trenchmode, the steering control 92 preferably operates in a trench steeringmode as characterized in FIG. 14. The steering control 92 preferablyoperates in a transport steering mode, as characterized in FIG. 15, whenthe transport mode is selected.

The relationship between the magnitude of the left and right track drive34 and 32 velocities in response to steering signals produced by thesteering control 92 when operating a track trencher 30 in a trench modeis illustrated in FIG. 14. The X-axis represents a preferred range ofoutput voltage signals produced by the steering control 92. The Y-axisrepresents a range of forward track drive velocities measured aspercentages of a selected track drive velocity relative to fullvelocity. Full track drive velocity is preferably determined by theparticular setting of the propel control 90. The steering control 92preferably produces an output voltage signal of 2.5 volts when set tothe zero setting 140, and results in steering the track trencher 30 in astraight direction. Output voltage signals between zero and 2.5 voltsare preferably associated with left turns, and output voltage signalsbetween 2.5 volts 5.0 volts are preferably associated with right turns.

Steering the track trencher 30 in a right direction while in the trenchmode is accomplished by turning the steering control 92 from the zerosetting 140 in a right direction toward the maximum right setting 144.As the steering control 92 is turned in the right direction, the lefttrack drive 34 is maintained at 100% of full propulsion, as indicated byline 156, while the right track drive 32 decelerates to a lowervelocity, as indicated by line 160. Similarly, steering a track trencher30 in a left direction is accomplished by turning the steering control92 in the left direction. A maximum left turn, for example, ischaracterized by the right track drive 32 being maintained at 100% offull velocity, as indicated by line 154, while the left track drive 34is held at zero velocity, as indicated at 142 of line 158.

In a preferred embodiment, the steering control 92 provides additionalfunctionality when operating the track trencher 30 in a transport modeof travel. Selection of a transport steering mode enables the left andright track drives 34 and 32 to operate in a counter-rotation mode foraccomplishing small radius turns. The term "counter-rotation" isgenerally understood in the art as referring to a method of turning atractor-type machine whereby one track drive is operated at a forwardvelocity while the other track drive is operated at a reverse velocity.

When a transport steering mode is selected, a high level ofmaneuverability is often desirable. In a preferred embodiment, thesteering control 92 provides steering in a manner similar to thatpreviously described with reference to FIG. 14 until a left or righttransition setting 146 or 148 is exceeded. Setting the steering control92 between the transition settings 146 and 148 and maximum settings 142and 144, respectively provides a proportional degree of counter-rotationsteering in a left and right direction for maneuvering a track trencher30. For illustrative purposes, the steering control 92 is showninitially set to a zero setting 140 at a 3 o'clock (3:00) position.Turning the track trencher 30 in the left direction is accomplished byrotating the steering control 92 between the 3:00 position and a maximumleft setting 142 at the 10:00 position. When the left transition setting146 at the 12:30 position is exceeded, counter-rotation steering isemployed for steering control 92 settings between the 12:30 position andthe 10:00 position. Turning the track trencher 30 in the right directionis accomplished in substantially the same manner.

Turning now to FIG. 15, the preferred steering characteristics of thesteering control 92 when operating a track trencher 30 in a transportsteering mode are illustrated. A right turn, for example, isaccomplished by turning the steering control 92 from the zero setting140 at the 3:00 position toward the maximum right setting 144 at the8:00 position. For steering control 92 settings between the zero setting140 and the right transition setting 148 at the 5:30 position, a rightturn is accomplished by maintaining the left drive track 34 at 100% offull velocity, shown as line 156, while the velocity of the right trackdrive 32 is reduced, shown as line 160.

The right transition setting 148 at the 5:30 position is characterizedby the left track drive 34 operating at 100% of full velocity while theright track drive 32 is held at zero velocity. Turning the steeringcontrol 92 beyond the right transition setting 148 results in theapplication of a negative velocity to the right track drive 32. Maximumright turning is accomplished by setting the steering control 92 to themaximum right setting 144 at the 8:00 position, wherein the left drivetrack 34 is maintained at 100% of full velocity in the forwarddirection, and the right drive track 32 is maintained at 100% of fullvelocity in the reverse direction, thereby employing 100% ofcounter-rotation steering.

As discussed previously, the steering control 92 typically producesoutput voltage signals between zero and 2.5 volts to accomplish leftturns, and output voltage signals between 2.5 and 5.0 volts toaccomplish right turns. The steering control 92 preferably producesoutput voltage signals of 1.25 and 3.75 volts when set to the left andright transition settings 146 and 148, respectively.

It is to be understood that the characteristic steering curvesillustrated in FIGS. 14 and 15 are provided for illustrative purposesonly, and do not constitute a limitation on the manner in which thenovel steering control 92 accomplishes steering of a track trencher. Forexample, FIGS. 14 and 15 illustrate a direct proportionality between thesteering control 92 output voltage signals and the left and right trackdrive 34 and 32 velocities. The left and right track drive velocitylines 158 and 160 may, for example, describe a polynomial functionalrelationship between the steering control 92 output voltage signals andthe left and right track drive 34 and 32 velocities. Further, the leftand right track drive velocity lines 154 and 156, being depictive of100% of full track drive velocity, may be adjusted to a velocity lessthan 100% of full velocity, and need not be held at a constantpercentage of full track drive velocity. Moreover, the left and righttransition settings 146 and 148 may be located at steering control 92settings other than the 12:30 and 5:30 positions illustrated in FIG. 13.

In another embodiment, the steering control 92, as shown in FIG. 20, maycomprise a steering lever, rather than a rotary steering control. A zerosetting 140 is associated with steering a track trench 30 in a straightdirection, with the left and right track drives 34 and 32 preferablyoperating at the same velocity. A right range of steering control 92settings is shown defined between a neutral setting 140 and a maximumright setting 144. The multiple mode steering control 92, shown in FIG.20, preferably functions in at least two modes, a trench steering modeand a transport steering mode.

Turning a track trencher in a right direction while operating in atrench steering mode is accomplished by moving the steering control 92between a zero setting 140 and a maximum right setting 144, while leftturns are accomplished by moving the steering control 92 between thezero setting 140 and a maximum left setting 142. Adjustment of the leftand right track drive 34 and 32 velocities in response to the setting ofthe steering control 92 shown in FIG. 20 is preferably similar to thatpreviously described with respect to FIG. 14.

Steering of the track trencher 30 using the steering control 92 shown inFIG. 20 while operating the track trencher 30 in a transport steeringmode is accomplished in a similar manner by moving the steering control92 to a desired left or right turning setting with respect to the zerosetting 140. Moving the steering control 92 beyond the left and righttransition settings 146 and 148 respectively invokes left and rightcounter-rotation steering preferably in a manner similar to thatpreviously described with respect to FIG. 15.

Turning now to FIG. 16, there is shown an exaggerated illustration ofthe novel manner in which the multiple mode steering control 92 steers atrack trencher 30 when transitioning between a forward and a reversedirection. As illustrated, the track trencher 30 includes an operator'sseat 54 from which an operator has set the steering control 92 to aright direction setting 266 in order to perform a 40 degree right turnwith respect to the positive X-axis 272. Moving in a forward direction,the track trencher will preferably follow a forward curved path 262.

Assuming that the operator sets the propel control 90 to a reversesetting while traveling on a forward curved path 262, the track trencher30 will operate in a reverse direction and preferably follow a reversecurved path 260. It is noted that the reverse curved path 260 wouldnormally be associated with a left steering control setting of 140degrees from the positive X-axis 272 (or +40 degrees from the negativeX-axis 274), which is 180 degrees from the originally selected 40 degreeforward right steering control setting 266 associated with the forwardcurved path 262. The steering control 92, however, preferably remains atthe same 40 degree forward setting 266 with respect to the positiveX-axis 272 to navigate the reverse curved path 260. It has beendetermined by the inventor that the unique 180 degree "flip-flop"operation of the steering control 92, e.g. the automatic 180 degreedirectional change in steering control 92 operation, upon transitioningbetween a forward and a reverse direction provides an operator with anintuitive or natural means for steering a track trencher 30.

The novel propel and steering controls 90 and 92 provide advantageouspropulsion and steering functions when controlling a track trencher 30in combination with a computer 182 as illustrated in FIG. 17. Althoughboth the propel control 90 and steering control 92 are shown ascomprising the control system in FIG. 17 and are generally discussedherein in combination with regard to operating a track trencher 30, itis to be understood that each of the controls 90 and 92 independentlyprovides advantageous functionality exclusive of the other. Theadvantages previously discussed when controlling propulsion of a tracktrencher 30 using the multiple mode propel control 90, for example, arerealized irrespective of the inclusion or exclusion of the steeringcontrol 92 from the system illustrated in FIG. 17. Similarly, theadvantages provided by the novel steering control 92 are realizablewithout incorporating the propel control 90 into such a control system.

In a preferred configuration, the left track drive 34 typicallycomprises a left track pump 38 coupled to a left track motor 42, and theright track drive 32 typically comprises a right track pump 40 coupledto a right track motor 44. Left and right track motor sensors 198 and192 are preferably coupled to the left and right track motors 42 and 44,respectively. The left and right track pumps 38 and 40, deriving powerfrom the engine 36, preferably regulate oil flow to the left and righttrack motors 42 and 44 which, in turn, provide propulsion for the leftand right track drives 34 and 32.

The attachment 46 preferably comprises an attachment motor 48 and anattachment control 98, with the attachment 46 preferably deriving powerfrom the engine 36. A sensor 186 is preferably coupled to the attachmentmotor 46. Actuation of the left track motor 42, right track motor 44,and attachment motor 48 is monitored by sensors 198, 192, and 186respectively. The output signals produced by the sensors 198, 192, and186 are communicated to the computer 182.

The computer 182, upon receiving a travel mode signal from the travelmode control 94, preferably modifies the functionality of the multiplemode steering control 92 and propel control 90 for operation in either atransport mode or a trench mode. The travel mode control 94 preferablyproduces a transport mode signal which is communicated to the computer182 when the transport mode is selected, and produces and communicatesto the computer 182 a trench mode signal when the trench mode isselected. The functionality of the steering control 92 and propelcontrol 90, in response to the state of the travel mode control 94, ismodified by the computer 182 to perform in a manner previously discussedhereinabove.

In response to the steering and propel control signals, the computer 182communicates control signals, typically in the form of control current,to the left and right track pumps 38 and 40 which, in turn, regulate thespeed at which the left and right track motors 42 and 44 operate. Theleft and right track motor sensors 198 and 192 communicate track motorsense signals to the computer 182 indicative of the actual speed of theleft and right track motors 42 and 44. Similarly, an engine sensor 208,coupled to the engine 36, provides an engine sense signal to thecomputer 182, thus completing a closed-loop control system for thetractor portion 45 of a track trencher 30. Those skilled in the art willrecognize that various known computer configurations will provide asuitable platform for effectuating propulsion and steering changes of atrack trencher 30 in response to the propel and steering signalsproduced by the multiple mode propel and steering controls 90 and 92.

The attachment 46 portion of a track trencher 30 includes an attachmentmotor 48, attachment control 98 and at least one attachment sensor 186.The attachment motor 48 preferably responds to instructions communicatedto the attachment control 98 from the computer 182. The actual output ofthe attachment motor 48 is monitored by the attachment sensor 186, whichproduces an attachment sense signal received by the computer 182.

In a preferred embodiment, the left and right track motor sensors 198and 192 are of a type generally referred to in the art as magnetic pulsepickups, or PPUs. The PPUs 198 and 192 transduce track motor rotationinto a continuous series of pulse signals, wherein the pulse trainpreferably represents the frequency of track motor rotation as measuredin revolutions-per-minute.

Another important advantage of a track trencher control systemincorporating the novel propel control 90 concerns the manner in which acomputer 182 maintains the left and right track drives 34 and 32 at atarget track drive propulsion level when operating a track trencher 30in a transport mode. When a transport mode of travel is selected, thepropel control 90 preferably produces a transport propel control signalwhich is representative of a target velocity for the left and righttrack motors 42 and 44, typically measured in revolutions-per-minute.Conversion of the transport propel signal into a target track motorvelocity may be accomplished by the propel control 90 itself or,preferably, by the computer 182.

The computer 182 typically compares the left and right track motor sensesignals respectively produced by the left and right PPU sensors 198 and192 to the target track motor propulsion level represented by thetransport propel signal. The computer 182 communicates the appropriatepump control signals to the left and right track pumps 38 and 40 inresponse to the outcome of the comparison to compensate for anydeviation between the actual and target track motor propulsion levels.

A more detailed description of the manner in which a computer systemtypically controls the propulsion of a track trencher 30 in response tothe control signals produced by the novel multiple mode propulsioncontrol 90 is provided hereinbelow with reference to FIGS. 21-24. FIGS.21 and 22 illustrate one embodiment of a control process by which thecomputer 182 controls the propulsion of a track trencher 30 whileoperating in a transport mode of travel. When a transport mode of travelis selected, as at step 340, the computer 182 converts an analog propelcontrol signal produced by the propel control 90 to a correspondingdigital transport propel signal at step 342.

Operating a track trencher 30 in an idle state, whereby no power isdelivered to the left and right track motors 42 and 44, is preferablyassociated with a transport propel signal equivalent to 2.5 volts aspreviously discussed with regard to FIGS. 9 and 10. The magnitude of thetransport propel signal is tested at step 344, and if found to beequivalent to 2.5 volts, no current is delivered to the electricaldisplacement controls (EDC) which respectively control the output levelof the left and right pumps 38 and 40. If the transport propel signal isgreater than 2.5 volts, as tested at step 348, the control currentdelivered to the left and right pump EDCs is preferably a positivecurrent. A transport propel signal less than 2.5 volts is preferablyassociated with a negative control current at step 352. The transportpropel signal is then converted by the computer 182 into a correspondingtarget track motor velocity at step 354. The computer 186 typicallyassociates the value of the digital transport propel signal to acorresponding target track motor velocity within a range of target trackmotor velocities previously stored in the computer 186. It is noted thatthe computer 182 typically calculates the necessary amount of controlcurrent delivered to the left and right track pumps 38 and 40 tomaintain the left and right track motors 42 and 44 at the target trackmotor velocity associated with the transport propel signal.

As shown in FIG. 22, the output of the PPU sensors 198 and 192 of theleft and right track motors 42 and 44, respectively, are sampled at step360, and actual track motor velocities are determined. Actual trackmotor velocity is compared to the target track motor velocity at step362, and if equivalent, the positive or negative control currentdelivered to the pump EDCs is maintained at step 364. If the actualtrack motor velocity is greater than the target motor velocity, as atstep 366, the computer 182 decreases the positive or negative currentsupplied to the pump EDCs at step 368. The control current supplied tothe pump EDCs is increased at step 370 if the actual track motorvelocity is less than the target track motor velocity determined at step366.

The multiple mode propel control 90, in combination with the computer182, provides additional functionality when operating a track trencher30 in a trench travel mode. When operating in a trench mode, thecomputer 182 preferably moderates propulsion of the left and right trackmotors 42 and 44 in response to the state of the engine 36. When thecomputer 182 receives a trench mode signal from the travel mode control94, the propel control 90 produces a trench propel signal that ispreferably representative of a target output level of the engine 36. Forexample, it may be desirable to operate a particular engine at 2,200RPMs during excavation. Accordingly, the propel control 90 at themaximum forward setting 112 will produce a trench propel signalrepresentative of a target engine output level of 2,200 RPMs. The outputlevel of the left and right track motors 42 and 44 will be adjusted bythe computer 182 so that the desired 2,200 RPM target engine outputlevel is maintained, preferably within a margin of tolerance.

In one embodiment, the computer 182 modifies the trench propel signal tomaintain the engine 36 at the target engine output level. As such, theoperator need not make any adjustments to the propel control 90 duringexcavation. Instead, the computer 182 modifies or scales the trenchpropel signal to an appropriate level to effectively increase ordecrease the propulsion level of the left and right track motors 42 and44 depending of the loading on the engine 36. The computer 182 thuscontrols the loading of the engine 36 by modifying the propulsion levelsof the left and right track drives 34 and 32 during excavation. Variousanalog and digital devices are known in the art for effectuating loadcontrol of an engine to maintain the engine at a constant speed undervarying load conditions. One such analog load controller is the ModelMCE101C Load Controller manufactured by Sauer Sundstrand. A suitabledigital device that can be adapted to perform engine load control is theModel DC2 Microcontroller, also manufactured by Sauer Sundstrand.

The left and right motor sensors 198 and 192 preferably communicateactual track motor speed, measured in revolutions-per-minute, to thecomputer 182. The engine 36 preferably includes an engine sensor 208which monitors the speed of the engine 36, also measured inrevolutions-per-minute, and communicates actual engine speed to thecomputer 182. Any deviation between the actual and target engine outputlevels is compensated for by the computer 182 communicating theappropriate pump control signals to the left and right track pumps 38and 40, which, in turn, regulate the speed at which the left and righttrack motors 42 and 44 operate.

Referencing now FIGS. 23 and 24, when a trench mode signal is receivedat step 300, an analog trench propel signal produced by the propelcontrol 90 is converted to a digital trench propel signal at step 302.If the trench propel signal is equivalent to 2.5 volts, as at step 304,no current is delivered to the EDCs of the left and right pumps 38 and40, respectively, at step 306. If the trench propel signal is greaterthan 2.5 volts, as at step 308, the control current delivered to thepump EDCs is a positive current, as at step 310. The control current isa negative current, at step 312, if the trench propel signal is lessthan 2.5 volts. At step 314, the trench propel signal is converted to acorresponding target engine speed, preferably by associating the trenchpropel signal to a corresponding engine speed previously stored in thecomputer 182.

The actual speed of the engine 36 is determined by sampling the enginesensor 208 at step 320. If the actual engine speed is equivalent to thetarget engine speed at step 322, the same level of positive or negativecurrent is delivered to the pump EDCs at step 324. If the actual enginespeed is greater than the target engine speed at 326, the positive ornegative control current delivered to the pump EDCs is decreased at step328. The positive or negative control current delivered to the pump EDCsis increased at step 330 if the actual engine speed is less than thetarget engine speed.

An embodiment of a process by which the computer 182, in response to thesteering signals produced by the steering control 92, effectuatessteering changes of a track trencher 30 is provided in FIGS. 25-32. Themultiple mode steering control 92 is preferably operable in a pluralityof travel modes, and at least a transport mode and a trench mode. FIGS.25-30 illustrate one embodiment of a steering control process forsteering a track trencher 30 operating in a transport travel mode, whileFIGS. 31 and 32 illustrate a steering control process for accomplishingsteering when operating in a trench travel mode.

As shown in FIGS. 25 and 26, the target left and right track motor 42and 44 velocities (V_(R) and V_(L)) are determined at step 390. Thetarget track motor velocities V_(R) and V_(L) are preferably derivedfrom the propel control signal received by the computer 182.Alternatively, an appropriate signal corresponding to a desired orselected propulsion level of the left and right track drives 34 and 32may be used as a basis for computing the target left and right trackmotor 42 and 44 velocities V_(R) and V_(L) at step 390. Upon receiving atransport mode signal at step 392, the computer 182 converts the analogsteering signal received from the steering control 92 to a digitalsteering signal at step 394.

If the steering signal is equivalent to 2.5 volts at step 396, the leftand right PPUs 198 and 192 of the left and right track motors 42 and 44,respectively, are sampled and actual velocities of the left and righttrack motors 42 and 44 are determined (V_(LA) and V_(RA)) at step 400.The actual left and right track motor velocities V_(LA) and V_(RA) arerespectively compared to the target left and right track motorvelocities V_(L) and V_(R) at steps 402 and 412. If the computed actualtrack motor velocities are equivalent to the target track motorvelocities, the level of current delivered to the left and right pump 38and 40 EDCs is held constant at steps 404 and 414. The control currentdelivered to the left and right pump EDCs is decreased at steps 408 and418, respectively, if the actual track motor velocities V_(LA) andV_(RA) are greater than the target left and right track motor velocitiesV_(L) and V_(R). The control current is increased respectively to theleft and right pump EDCs at steps 410 and 420 when the actual trackmotor velocities V_(LA) and V_(RA) are less than the target track motorvelocities V_(L) and V_(R).

The control process shown in FIG. 27 further illustrates the novelsteering characteristics of the steering control 92 when the steeringcontrol 92 is between a zero setting 140 and a right transition setting148 in order to effect a right turn. Between these settings, a steeringcontrol signal will preferably range between 2.5 volts and 3.75 volts.When a steering control signal is determined by the computer 182 to bewithin this range at step 440, the left track motor 42 is maintained at100% of the target track motor velocity V_(L) at step 442. To effect aright turn, the positive current delivered to the right pump 40 EDC isdecreased at step 444, and the actual deceleration of the right trackmotor 44 is determined by sampling the right PPU at step 446. Asdiscussed previously with respect to FIG. 14, the degree to which theright track motor 44 decelerates is preferably directly proportional tothe steering signal produced by the steering control 92 between theranges of 2.5 volts and 3.75 volts.

At step 448, for example, the computer 182 preferably computes a newtarget right track motor 44 velocity in response to the steering control92 setting by multiplying the original right track motor velocity V_(R)by a scaling factor. It is noted that the value of the scaling factor ispreferably a function of the equation defining the characteristicsteering curve 160 illustrated in FIG. 15, and reflects the percentchange in the value of the steering control signal (SS) from a maximumat 2.5 volts to a minimum at 5.0 volts. If the actual right track motorvelocity V_(RA) is equivalent to the new target right track motorvelocity computed at 448, the level of positive control currentdelivered to the right pump 44 EDC is maintained at step 450. If theactual right track motor velocity V_(RA) is less than the new targetright track motor velocity V_(R), the positive current delivered to theright pump 44 EDC is increased at step 454, and, if the steering control92 setting has not been changed, the right PPU is again sampled todetermine the actual velocity V_(RA) in response to the increasedpositive control current at step 446. The positive control currentdelivered to the right pump 44 EDC is decreased at step 444 in the eventthat the actual right track motor velocity V_(RA) is greater than thenew target right track motor velocity.

Moving the steering control 92 further in a right direction beyond theright transition setting 148 causes the novel steering control system toemploy counter-rotation steering for effectuating a right turn.Counter-rotation steering in a right direction is preferably associatedwith steering control 92 output signals between 3.75 volts and 5.0volts, as shown in FIGS. 15 and 28. For steering control 92 signalswithin this range, the left track motor 42 is preferably maintained at100% of full left track motor velocity V_(L) at step 462. It is notedthat the right track motor 44 is operated in a reverse direction withrespect to the left track motor 42 for effectuating a right turnemploying counter-rotation steering. As such, a negative current isapplied to the right pump 40 EDC at step 464, causing the right trackmotor 44 to operate in a reverse direction. The actual right track motor44 velocity, both magnitude and forward or reverse direction, V_(RA) isdetermined by sampling the right track motor PPU sensor 192 at step 466.

The computer, at step 468, preferably computes a new target velocity forthe right track motor 44 in response to the steering control 92 settingby multiplying the original right track motor velocity V_(R) by ascaling factor. For clarity, the absolute values of the computed resultsare compared at step 468, although the computation of the relativedifference between the actual and target right track motor velocitiesmay be accomplished in an alternative manner. If the actual and newtarget right track velocities are equivalent, no modification is made tothe level of negative control current delivered to the right pump EDC,as indicated at step 470. If the absolute value of the actual righttrack motor velocity V_(RA) is greater than the absolute value of thenew target right track motor velocity, the level of negative controlcurrent supplied to the right pump EDC is decreased at step 474. Thecomputer 182 effectuates an increase in the negative control currentdelivered to the right pump EDC at step 464 when the absolute value ofthe actual right track motor velocity is less than the absolute value ofthe new target right track motor velocity.

FIGS. 29 and 30 illustrate a sequence of steering control process stepsto effectuate left turning of a track trencher 30 while operating in atransport travel mode. The process by which turning and counter-rotationturning of a track trencher 30 in a left direction is accomplished ispreferably substantially similar to that previously described withregard to accomplishing right turns as illustrated in FIGS. 27 and 28.The scaling factors and the equations to compute a new target left trackmotor velocity, however, are, of course, different from those foraccomplishing right turns.

The multiple mode steering control 92 provides different functionalitywhen steering a track trencher 30 in a trench travel mode. In oneembodiment, as illustrated in FIGS. 14, 31, and 32, steering a tracktrencher 30 in a straight direction is associated with a steeringcontrol 92 signal of 2.5 volts, plus or minus a tolerance factor. Thecomputer 182, at step 520, preferably associates steering control 92signals in excess of 2.5 volts with steering a track trencher is a rightdirection. The left track motor 42 is maintained at 100% of the targetvelocity V_(L) at step 522, and the positive control current supplied tothe right pump EDC is decreased at step 524. The actual right trackmotor 44 velocity V_(RA) is determined from sampling the right PPUsensor 192 at step 526, and compared to the new target right track motor44 velocity at step 528. It is noted that a scaling factor, indicated atstep 528 as ((5.0-SS)/2.5), is formulated from the equation of the line160 describing a preferred relationship between the steering control 92output signals and the associated change in the velocity of the righttrack motor 44.

The level of positive control current supplied to the right pump EDC ismaintained at step 530 as long as the actual right track motor 44velocity V_(RA) is equivalent to the new target right track motor 44velocity. The positive control current is either increased at step 534or decreased at step 524 depending on the outcome of the comparison ofthe actual and new target right track motor velocities performed by thecomputer 182 at step 532. Steering at track trencher 30 in a leftdirection is accomplished in substantially the same manner as previouslydescribed with reference to the steering control process illustrated inFIG. 31. It is noted that counter-rotation steering is preferablyunavailable when turning a track trencher 30 in a trench mode ofoperation. Thus, steering a track trencher 30 in a trench mode of travelis accomplished by decreasing the level of positive current supplied tothe pump EDC of the appropriate track drive.

One significant advantage of the novel propulsion and steering controlsystem illustrated in FIG. 17 concerns the manner in which operationalinformation regarding the track trencher 30 is communicated to anoperator. A display 100, shown in FIG. 7, is coupled to the computer182, and preferably communicates messages indicative of operatingstatus, diagnostic, calibration, fault, safety, and other relatedinformation to the operator. The display 100 provides quick, accurate,and easy-to-understand information to an operator by virtue of theinterpretive power of the computer 182 which acquires and processes datafrom a plurality of track trencher sensors. As such, an operator neednot mentally record, interpret, and assess the relative importance of aplurality of prior art analog display instrument readings in order toefficiently and safely operate a track trencher 30. Incorporating thedisplay 100 into the control scheme and providing an operator with aplurality of immediately understandable informational messagesdramatically and fundamentally alters the manner in which a tracktrencher 30 is operated.

The display 100 is preferably a liquid crystal display, although othersuitable types of displays may be employed, such as a cathode ray tube.A message selection switch 99, proximate the display 100, provides meansfor selecting a plurality of informational messages, such as those shownin FIG. 18. Toggling the message selection switch 99 preferably resultsin displaying additional informational messages on the display 100.

Provided in FIG. 18 are several examples of the types of informationalmessages which can be communicated to the operator of a track trencher30 when employing the display 100. Message 210, for example, indicatesthat the track trencher 30 is operating in a transport mode at avelocity of 98 FPM, with the speed range control 96 set to a lowsetting. The message 210 further indicates that the track trencher 30 isperforming a left turn at 10% of the maximum left turning capability.The particular attachment 46 coupled to the track trencher 30 isindicated as a chain, a short form of the term ditcher chain 50. Theditcher chain 50 is currently inoperative as indicated by the 0% of fullattachment 46 output. It should be appreciated that this information,particularly the speed and turning status information of the tracktrencher 30, was heretofore unavailable to the operator controlling atrack trencher 30 using a prior art control panel 62. Instead, onlycrude estimates were figured by the skilled operator after monitoringand interpreting the state of various analog display instruments.

The informational status message 211 indicates that the track trencher30 is currently operating in the low range of the trench mode and at arate of 1.3 FPM. The ditcher chain 50 is indicated as currentlyoperating at 72% of full attachment 46 output, and the track trencher 30is straight tracking with no left or right turning component.

Various other status messages may be communicated to the operator, suchas message 212, wherein the current engine speed is indicated as 2,200RPM, the engine has been operated for a total elapsed operating time of332.1 hours, and the battery is indicated at operating at 12.2 volts. Itis to be understood that the status messages illustrated in FIG. 18 areprovided for illustration only, and do not represent limitations on thenature of information communicated over the display 100.

In addition to status messages describing the state of variousoperational parameters of a track trencher 30, fault conditionsresulting from anomalous operating conditions are also communicated tothe operator over the display 100. Typically, a track trencher 30employs a plurality of sensors in addition to those shown in FIG. 17.Other mechanical or electrical components comprising the track trencher30 typically include one or more sensors for monitoring the operatingcondition of the particular component. The throttle 206 of the engine36, for example, may include a throttle sensor which monitors thevoltage or other parameter of the throttle control 206. A malfunction ofthe throttle control 206 may be communicated to the operator as a faultmessage 213 indicating that an unacceptable throttle sensor voltagesignal has been detected.

A malfunctioning left track motor sensor 198 may be communicated as afault message 214, wherein the left track PPU signal is lost or notcurrently being received by the computer 182. Other fault messages maybe indicative of more severe anomalous operating conditions, such asexcessively low oil pressure 215 or excessively high water or coolanttemperature 216. Moreover, various instructional messages may becommunicated to the operator when performing routine maintenance,repair, and calibration of the track trencher 30. Further, the display100 is employed to provide a user-interactive environment whichsubstantially enhances the operation and routine maintenance of thetrack trencher 30, and increases the quality and quantity of informationcommunicated to the operator.

One important feature of novel display and control system concerns asafety feature by which the engine 36 is automatically shutdown when asevere anomalous operating condition is detected. Two such severe engineconditions are indicated by fault messages 215 and 216, wherein anexcessively low oil pressure or an excessively high water temperature isdetected. Upon detecting a severe anomalous operating condition, thecomputer 182 will preferably initiate an engine shutdown sequence inwhich the engine is automatically shutdown after a predetermined amountof time.

The warning messages 216 and 217, illustrated in FIG. 18, indicate thatthe engine will shutdown in 30 seconds due to detection of anexcessively high water temperature, thereby giving the operatorinformation with regard to both the amount of time remaining until theengine is shutdown, as well as the nature of the anomalous operatingcondition. The computer 182 preferably controls a fuel control 204 thatregulates fuel to the engine 36. Upon termination of the engine shutdownsequence, indicated by the expiration of the allotted 30 seconds, thecomputer 182 instructs the fuel control 204 to discontinue deliveringfuel to the engine 36, thus resulting in the shutdown of the engine 36.

Another important advantage concerns various features which enhance theoperator's safety. In one embodiment, an operator's seat sensor 200,preferably installed in the operator's seat 54, is coupled to thecomputer 182. The operator's seat sensor 200 is preferably a normallyclosed switch, or other type of switch which monitors the presence ofthe operator on the operator's seat 54.

Alternatively, the sensor 200 may be adapted for sensing the presence ofthe operator within a predetermined area, such as an area designated forcontrolling the track trencher 30, and communicating a presence signalto the computer 182 whenever the operator leaves the predetermined area.A force sensor, for example, provided in a mat covering the floorportion of the predetermined control area, or a light beam presencedetector may be suitable alternative means for monitoring the presenceof an operator in the control area portion of a track trencher 30.

Upon receiving a presence signal from the operator's seat sensor 200,the computer 182 preferably communicates a disable control signal thatinterrupts or otherwise disables propulsion of the left and right trackdrives 34 and 32. It is noted that the interruption of propulsion to thetrack drives 34 and 32 may be accomplished by shutting down the engine36. Preferably, the engine 36 remains operating when the computer 182receives a presence signal, with the power delivered to the track drives34 and 32 being interrupted or disabled. As such, stress on the engine36 is dramatically reduced over time. The status of such an interruptionis preferably communicated to an operator over the display 100, as wellas instructional messages as to the proper steps to continue with normaltrack trencher 30 operation.

In one embodiment, normal operation of the track trencher 30 ensues whenthe operator returns to the operator's seat 54 within a predeterminedamount of time after the seat sensor 200 initially produces a presencesignal. For example, should the operator leave the operator's seat 54but return to the seat 54 within six seconds, propulsion of the left andright track drives 34 and 32 is unaffected. In addition to disabling theleft and right track drives 34 and 32, the computer 182, upon receivinga presence signal, preferably interrupts all attachment 46 activity.

It will, of course, be understood that various modifications andadditions can be made to the preferred embodiments discussed hereinabovewithout departing from the scope or spirit of the present invention.Accordingly, the scope of the present invention should not be limited bythe particular embodiments discussed above, but should be defined onlyby the claims set forth below and equivalents thereof.

What is claimed is:
 1. An information system for a track trencher,comprising:a track trencher including a left track drive, a right trackdrive, and an engine coupled to the left and right track drives; dataacquisition means for acquiring data indicative of an operatingcondition of one of the left and right track drives and the engine, andfor producing a signal corresponding to a message indicative of theoperating condition; and display means, coupled to the data acquisitionmeans, for receiving the signal and communicating the message to anoperator.
 2. A system claimed in claim 1, wherein the data acquired bythe data acquisition means includes data indicative of an operatingcondition of a trenching attachment coupled to the track trencher.
 3. Asystem claimed in claim 2, wherein the display means comprises adisplay, and the data acquisition means includes means for communicatingover the display a message indicative of an operating condition of thetrenching attachment.
 4. A system claimed in claim 1, wherein thedisplay means comprises a display, and the data acquisition meansincludes means for communicating over the display a message indicativeof an operating condition of the left and right track drives.
 5. Asystem claimed in claim 1, wherein the display means comprises adisplay, and the data acquisition means includes means for communicatingover the display a message indicative of an operating condition of theengine.
 6. A system claimed in claim 1, wherein:the display meanscomprises a display; the data acquisition means comprises means forinterpreting the data acquired from the left and right track drives intoa message indicative of an operating condition of the left and righttrack drives; and the data acquisition means comprises means forcommunicating the message to an operator over the display.
 7. A systemclaimed in claim 1, wherein:the display means comprises a display; thedata acquisition means comprises means for interpreting the dataacquired from the engine into a message indicative of an operatingcondition of the engine; and the data acquisition means comprises meansfor communicating the message to an operator over the display.
 8. Asystem claimed in claim 1, wherein:the display means comprises adisplay; the data acquisition means comprises means for interpreting thedata acquired from a trenching attachment coupled to the track trencherinto a message indicative of an operating condition of the trenchingattachment; and the data acquisition means comprises means forcommunicating the message to an operator over the display.
 9. A systemclaimed in claim 1, wherein the acquired data is provided by a sensorcoupled to at least one of the left and right track drives and engine.10. A system claimed in claim 9, wherein the left and right track drivesinclude a sensor for respectively sensing the speed of the left andright track drives, the sensor comprising a magnetic pulse pickup.
 11. Asystem claimed in claim 1, wherein the display means includes means fordisplaying the message as alphanumeric characters.
 12. A system claimedin claim 1, wherein the display means comprises a liquid crystaldisplay.
 13. A system claimed in claim 1, wherein the display meanscomprises a cathode ray tube.
 14. A system claimed in claim 1, whereinthe display means includes means for displaying a message indicative ofthe speed of the track trencher.
 15. A system claimed in claim 1,wherein the display means includes means for displaying a messageindicative of the speed of the left track drive and the speed of theright track drive.
 16. A system claimed in claim 15, wherein the displaymeans includes means for displaying a message indicative of the relativedifference between the velocity of the left and right track drives. 17.A system claimed in claim 1, wherein the display means includes meansfor displaying a message indicative of an anomalous track trencheroperating condition.
 18. A system claimed in claim 17, wherein the dataacquisition means includes means for retrievably storing the dataassociated with the anomalous track trencher operating condition.
 19. Asystem claimed in claim 17, wherein the display means includes means fordisplaying a message indicative of imminent engine shutdown.
 20. Asystem claimed in claim 1, wherein the display means includes means fordisplaying a plurality of instructional messages to an operator, theinstructional messages being associated with instructions for adjustingan operation of the track trencher.
 21. A system claimed in claim 1,wherein the display means includes means for displaying a menu to anoperator, the menu providing means for adjusting an output level of theengine of the track trencher.
 22. A system claimed in claim 1, whereinthe display means includes means for displaying a plurality of messagesto an operator.
 23. An information system for a track trencher,comprising:a track trencher including a left track drive, a right trackdrive, and an engine coupled to the left and right track drives; acomputer for receiving signals produced by sensors respectively coupledto the left and right track drives and the engine, the computerproducing a signal corresponding to a message associated with the signalproduced by at least one of the sensors; a display coupled to thecomputer; and a control, Coupled to the computer, for selecting from aplurality of messages the message associated with the signal produced bythe at least one of the sensors for communication over the display. 24.A system claimed in claim 23, comprising:a trenching attachment coupledto the track trencher; and a sensor coupled to the trenching attachment;wherein the computer produces a signal corresponding to a messageassociated with a signal produced by the sensor coupled to the trenchingattachment.
 25. A system claimed in claim 23, wherein the computerproduces a signal corresponding to a message associated with a signalproduced by the sensors respectively coupled to the left and right trackdrives.
 26. A system claimed in claim 23, wherein the computer producesa signal corresponding to a message associated with a signal produced bythe sensor coupled to the engine.
 27. A system claimed in claim 23,wherein the computer produces a signal corresponding to a messageassociated with an anomalous track trencher operating condition forcommunication over the display.
 28. A system claimed in claim 23,wherein the display communicates a plurality of track trencher operatingcondition messages to an operator.
 29. A method for communicatinginformation for a track trencher, including the steps of:providing anengine coupled to a left and right track drive of the track trencher;acquiring data indicative of an operating condition of the left andright track drives of the track trencher; interpreting the acquired datato an associated informational message; and displaying the informationalmessage to an operator of the track trencher.
 30. A method as claimed inclaim 29, including the step of displaying the informational message asalphanumeric characters.
 31. A method as claimed in claim 29, includingthe further steps of:acquiring data indicative of an operating conditionof the engine; interpreting the engine data to an associatedinformational engine message; and displaying the informational enginemessage to an operator of the track trencher.